Genome-wide analysis suggests the potential role of lncRNAs during seed development and seed size/weight determination in chickpea

Identification of lncRNAs regulating seed traits in Brassica juncea and development of a comprehensive seed omics database

Brassica juncea is a crucial oilseed crop, and its seeds possess high economic value as they are a source of edible oil. In order to understand the role of long non coding RNAs (lncRNAs) in the regulation of seed development, we carried out computational analysis using transcriptome data of developing seeds of two contrasting genotypes of B. juncea, Pusajaikisan (PJK) and Early Heera 2 (EH2). The seeds were sampled at three stages, 15, 30, and 45 days after pollination. We identified 1,539 lncRNAs, of which 809 were differentially expressed. We also carried out extensive characterization and functional analysis of seed lncRNAome. The expression patterns were analysed using k-means clustering, and the targets were analysed using pathway, transcription factor, and GO enrichment, as well as ortholog information. We shortlisted a total of 25 robust lncRNA candidates for seed size, oil content, and seed coat color. We also identified 4 lncRNAs as putative precursors of miRNAs regulating seed development. Moreover, a total of 28 miRNA-lncRNA-mRNA regulatory networks regulating seed traits were identified. We also developed a comprehensive database, (BrassIca juncea database or "BIJ" ( https://bij.cuh.ac.in/ ), which provides seed omics as well as other functional genomics and genetics data in an easily accessible form. These candidate lncRNAs are suitable for including in crop improvement programs through molecular breeding, as well as for future validations through genome editing. Together, the knowledge of these candidate lncRNAs and availability of BIJ database shall leverage the crop improvement efforts in B. juncea.

Systematic profiling and analysis of growth and development responsive DE-lncRNAs in cluster bean (Cyamopsis tetragonoloba)

Long non-coding RNAs (lncRNAs) play crucial role in regulating genes involved in various processes including growth & development, flowering, and stress response in plants. The study aims to identify and characterize tissue-specific, growth & development and floral responsive differentially expressed lncRNAs (DE-lncRNAs) in cluster bean from a high-throughput RNA sequencing data. We have identified 3309 DE-lncRNAs, with an average length of 818 bp. Merely, around 4 % of DE-lncRNAs across the tissues were found to be conserved as rate of evolution of lncRNAs is high. Among the identified DE-lncRNAs, 204 were common in leaf vs. shoot, leaf vs. flower and flower vs. shoot. A total of 60 DE-lncRNAs targeted 10 protein-coding genes involved in flower development and initiation processes. We investigated 179 tissue-specific DE-lncRNAs based on tissue specificity index. Three DE-lncRNAs: Cb_lnc_0820, Cb_lnc_0430, Cb_lnc_0260 and their target genes show their involvement in floral development and stress mechanisms, which were validated by Quantitative real-time PCR (qRT-PCR). The identified DE-lncRNAs were expressed higher in flower bud than in leaf and similar expression pattern was observed in both RNA-seq data and qRT-PCR analyses. Notably, 362 DE-lncRNAs were predicted as eTM-lncRNAs with the participation of 84 miRNAs. Whereas 46 DE-lncRNAs were predicted to possess the internal ribosomal entry sites (IRES) and can encode for small peptides. The regulatory networks established between DE-lncRNAs, mRNAs and miRNAs have provided an insight into their association with plant growth & development, flowering, and stress mechanisms. Comprehensively, the characterization of DE-lncRNAs in various tissues of cluster bean shed a light on interactions among lncRNAs, miRNAs and mRNAs and help understand their involvement in growth & development and floral initiation processes. The information retrieved from the analyses was shared in the public domain in the form of a database: Cb-DElncRNAdb, and made available at http://backlin.cabgrid.res.in/Cb-DElncRNA/index.php, which may be useful for the scientific community engaged cluster bean research.

Long Non-Coding RNAs: Discoveries, Mechanisms, and Research Strategies in Seeds

Seeds provide nutrients for the embryo and allow for dormancy in stressed environments to better adapt the plant to its environment. In addition, seeds are an essential source of food for human survival and are the basis for the formation of food production and quality. Therefore, the research on the genetic mechanism of seed development and germination will provide a theoretical basis and technical support for the improvement of crop yield and quality. Recent studies have shown that long non-coding RNAs (lncRNAs) occupy a pivotal position in seed development and germination. In this review, we describe the key processes in seed biology and examine discoveries and insights made in seed lncRNA, with emphasis on lncRNAs that regulate seed biology through multiple mechanisms. Given that thousands of lncRNAs are present in the seed transcriptome, characterization has lagged far behind identification. We provide an overview of research strategies and approaches including some exciting new techniques that may uncover the function of lncRNAs in seed. Finally, we discuss the challenges facing the field and the opening questions. All in all, we hope to provide a clear perspective on discoveries of seed lncRNA by linking discoveries, mechanisms, and technologies.

Emerging roles of long non-coding RNAs in regulating agriculturally important seed traits

Seeds have enormous economic importance as source of calories, nutrition, edible oil, and biofuels. Therefore, seed traits like seed size and shape, weight, micronutrient content, oil content, quality, post-harvest sprouting, etc., are some of the main targets in crop improvement. Designing the strategies for their improvement benefits heavily from understanding the regulatory aspects of seed development. Recent studies indicate that long non-coding RNAs (lncRNAs) are one of the important regulators of seed development. They played a significant role in crop domestication by influencing seed traits. LncRNAs are conventionally defined as non-coding RNAs greater than 200 bp in length but lacking protein coding potential. Here we highlight the emerging pieces of evidence of lncRNA-mediated regulation of seed development through diverse mechanisms, for instance, by acting as target mimics or precursors of regulatory small RNAs or through chromatin remodeling and post-transcriptional repression. We also enumerate the insights from high-throughput transcriptomic studies from developing seeds of cereal, oilseed, biofuel, and pulse crops. We highlight the lncRNA candidates and lncRNA-mediated regulatory networks regulating seed development and related agronomic traits. Further, we discuss the potential of lncRNAs for improvement of agriculturally important seed traits through marker-assisted breeding and/or transgenic approaches.

An integrated transcriptome mapping the regulatory network of coding and long non-coding RNAs provides a genomics resource in chickpea

Large-scale transcriptome analysis can provide a systems-level understanding of biological processes. To accelerate functional genomic studies in chickpea, we perform a comprehensive transcriptome analysis to generate full-length transcriptome and expression atlas of protein-coding genes (PCGs) and long non-coding RNAs (lncRNAs) from 32 different tissues/organs via deep sequencing. The high-depth RNA-seq dataset reveal expression dynamics and tissue-specificity along with associated biological functions of PCGs and lncRNAs during development. The coexpression network analysis reveal modules associated with a particular tissue or a set of related tissues. The components of transcriptional regulatory networks (TRNs), including transcription factors, their cognate cis-regulatory motifs, and target PCGs/lncRNAs that determine developmental programs of different tissues/organs, are identified. Several candidate tissue-specific and abiotic stress-responsive transcripts associated with quantitative trait loci that determine important agronomic traits are also identified. These results provide an important resource to advance functional/translational genomic and genetic studies during chickpea development and environmental conditions.

A full-length transcriptome and expression atlas of protein-coding genes and long non-coding RNAs is generated in chickpea. Components of transcriptional regulatory networks and candidate tissue-specific transcripts associated with quantitative trait loci are identified.